If an asteroid was on a collision course with Earth, like the one that wiped out the dinosaurs, could we stop it?
That's what NASA's Double Asteroid Redirection Test is on a mission to find out.
The world's first full-scale mission to test technology for defending Earth against potential asteroid collisions has hit its target — now scientists will be watching closely to see if it worked.
Here's what you need to know.
What is DART?
The Double Asteroid Redirection Test — or DART — is a small spacecraft on a one-way mission to try to send an asteroid off-course through kinetic impact.
DART will plough into a little moonlet called Dimorphos at high speed, aiming to nudge the space boulder off course just enough that if it was headed towards Earth, it would miss us.
When we say "little", we mean roughly the size of a football stadium.
Dimorphos is orbiting around another asteroid, which is about five times bigger, called Didymos.
Dimorphos isn't considered a risk to Earth, but scientists decided it was a good candidate for the test mission because of its dual-asteroid configuration, which makes it ideal for observing and recording the results of the impact.
Another advantage is its close proximity to Earth — meaning ground-based telescopes will be able to record what happens — and again, when we say "close proximity", we're talking up to 11 million kilometres away.
Can I watch the moment of impact?
NASA live-streamed the DART spacecraft hitting Dimorphos on Tuesday morning Australian time, so you can see it approaching frame-by-frame.
That vision was captured by DART's Didymos Reconnaissance and Asteroid Camera for Optical navigation (or DRACO), the only instrument attached to the spacecraft, which was first activated about a week after it was launched in September last year.
DRACO's jobs are to:
- Support DART's navigation and keep it on target
- Measure the size and shape of Dimorphos
- Provide detailed views of the location of impact
DART also has its own "mini-photographer" in the form of a Light Italian CubeSat for Imaging Asteroids, otherwise known as LICIACube, up there alongside it.
We'll be able to see the other angles that LICIACube captures soon.
LICIACube was connected to DART when it launched from Earth but deployed from the spacecraft a couple of weeks ago to document the impact on the asteroid.
NASA says LICIACube will fly past Dimorphos a few minutes after DART impacts and is supposed to:
- Confirm DART's impact
- Capture images of the crater DART leaves on the asteroid
- Capture images of the opposite hemisphere of Dimorphos that can't be seen from DART
The images captured by LICIACube and data from ground-based telescopes will be used by scientists to establish planetary defence strategies, should we ever need them.
How did we get to this point?
The DART spacecraft was launched in November 2021 from the Vandenberg Space Force Base in California, and has taken 10 months to travel to the asteroid it's on track to hit.
It was built by the Johns Hopkins Applied Physics Laboratory (APL) in Maryland, and it's been years in the making to get this far.
Scientists have been studying asteroids, including Dimorphos, for decades, and NASA established its Planetary Defense Coordination Office in 2016.
The DART concept was refined as part of that project, and entered a preliminary design phase in July 2017.
APL says DART's navigations systems were built off the back of "decades of missile-guidance expertise".
DART won't be coming back after impact — but it paves the way for the planned launch of the Hera mission in 2024, which is set to deliver detailed data on both Didymos and Dimorphos.
APL says DART and Hera are "designed and operated independently, but their combination will boost the overall knowledge return to a significant degree".
Wait, is this the mission that's been delayed a few times?
You might be thinking of Artemis I — which has failed to launch three times in the last month.
Artemis I is the unmanned mission set to test NASA's Space Launch System before Artemis II — a crewed flight — takes humans back to the Moon in 2023.
Artemis I was due for its third attempt at launching this week, but the call was made to postpone it again due to a tropical storm in the area.
NASA made the decision on Monday to roll Artemis I back into the Kennedy Space Center's Vehicle Assembly Building to "protect it from possible lightning, damaging winds, and possible debris".
That process is set to take between eight and 12 hours, and was scheduled to start at 11pm on Monday night (local time).
"Managers met Monday morning and made the decision based on the latest weather predictions associated with Hurricane Ian, after additional data gathered overnight did not show improving expected conditions for the Kennedy Space Center area," NASA said in a blog post.
"The decision allows time for employees to address the needs of their families and protect the integrated rocket and spacecraft system.
"The time of first motion also is based on the best-predicted conditions for rollback to meet weather criteria for the move."
The next window for a launch attempt is on October 3, weather and equipment-depending.